Suspended electric trolleys (electrified hoists, hoists and beam cranes) are used for lifting and moving loads and machine parts during installation and repair work inside industrial premises. Beam cranes are smaller than overhead cranes, which reduces the size of industrial buildings, and their maintenance does not require qualified personnel.
Suspended electric trolleys are designed for lifting and moving loads at production facilities along a strictly defined path.
To drive the load lifting mechanism at a speed of 6.5 - 6.9 m/s, an asynchronous motor with increased slip type AOS-32-4M is used (power 1.4 kW at 1320 rpm and duty cycle = 25%). The upward movement of the hook is limited by a limit switch.
To drive the running trolley, an electric hoist uses an asynchronous
electric motor type TEM - 0.25 (power 0.25 kW at 1410 rpm and duty cycle = 25%) The movement of the hoist along the beam in both directions is limited by mechanical stops.
The beam crane can move along the production premises, driven by an electric motor with a squirrel cage or wound rotor. The crane-beam bridge, which has a moving mechanism with an electric drive, is made in the form of a single beam along which an electric trolley moves.
To drive suspended electric trolleys, three-phase asynchronous motors with a squirrel-cage rotor are used, and only with a large load capacity and the need to regulate speed and smooth “landing” of loads - asynchronous motors with a wound rotor.
Due to the lack of low speed required for smooth landing of loads or precise stopping of the crane beam, the worker has to periodically turn on and off the electric motors, and this increases the number of starts and causes heating of the windings, and also reduces the wear resistance of the contacts. Therefore, some crane beams have electric drives for lifting and moving with two operating speeds: nominal and reduced, which are ensured by using two-speed asynchronous motors instead of single-speed ones or an additional microdrive.
Suspended electric trolleys with a low travel speed (0.2 - 0.5 m/s), driven by squirrel-cage motors, are usually controlled from the floor (ground) level using pendant push-button stations. In suspended trolleys and crane beams with an operator's cabin (at a movement speed of 0.8 - 1.5 m/s), wound-rotor motors are controlled using controllers.
The electric motors of the crane beams are controlled using reversible magnetic starters and start buttons suspended on a flexible armored cable.
The voltage to the coils and contacts of the contactors for lifting KM1 (Fig. 4), lowering KM2, moving forward KMZ and backward moving KM4 is supplied through a circuit breaker and cable or contact wires. The upward movement of the lifting device is limited by the limit switch SQ.
Figure 3.1 Electrical circuit diagram of the crane beam
Blocking of reversing motor contactors from simultaneous activation is carried out by double-circuit buttons and mechanical blocking of the contactors themselves (or by the contactor break contacts).
On electric hoists and overhead cranes, they do not use bypassing of the starting buttons with the corresponding closing blocking contacts of the contactors, preventing the possibility of the hoist continuing to operate after the operator releases the pendant push-button station. Simultaneously with the lifting motor, the electromagnet UA is turned on, opening the brake.
The operating mode of overhead crane beam engines depends on their purpose. If loads are moved to overhead cranes on short distances, then the engines operate in a shamefully short-term mode (for example, on carts serving areas of workshops or warehouses).
For crane beams transporting loads across the plant territory over relatively long distances, the operating modes of the lifting and moving motors are different: the former are characterized by a short-term mode, and the latter by a long-term mode. The power of the motors for lifting and moving electric hoists, hoists and crane beams is determined in the same way as for the motors of overhead crane mechanisms.
There are modifications of the crane with different span lengths, hook lifting heights and product lifting capacity. In this case, the crane span can vary from 4.5 to 22.5 m or more.
The crane's service area allows it to cover the maximum height of the workshop; The simplicity of the crane beam design allows it to be used for the mechanization of loading and unloading operations in mechanical engineering and warehousing.
The crane beam is intended for operation indoors or under a canopy at an ambient temperature of -20 to +40 degrees C (from -40 to +40 degrees C as agreed with the customer). The crane is powered from three-phase network alternating current voltage 380 V and frequency 50 Hz. The construction height of the crane depends on the construction height of the hoist and the height of the metal structure of the crane.
Control is carried out by the operator, from a pendant console (from the floor) or a remote control remote control Additional options: Radio control up to 100 m, IP65, lightweight, battery powered. Frequency converter for smooth acceleration and the ability to change the speed of cargo transportation. Load limiter (on the hoist). Brake on the movement mechanism Micro speeds for lifting (depending on the selected hoist)
Specifications
Load capacity, t 1; 2; 3.2; 5; 10; 12.5; 16.0t.
Lifting height, m 6.0 - 36.0 and above
Span, m 4.5-22.5
Operating mode according to: - GOST 25835 3M
Lifting speed, m/min (depending on the choice of hoist) micro/main. 4, 6, 8, 12,16
1/4; 2/8; 3/12; 4/16
Crane travel speed, m/min 20.0; 24.0; 32.0
arbitrary speed (0-32.0)
Hoist movement speed, m/min
(depending on the choice of hoist) 12; 15; 20; 32;
12/4; 15/5; 20/6; 32/10
Climatic performance:
Standard
Low temperature
from -20C to +40C
from -40C to +40C
The operating cycle of an overhead support and suspension crane consists of three stages:
Grabbing and/or securing cargo;
The main working stroke is lifting, moving cargo, unloading;
Free idling without load - return of the lifting mechanism to its original position.
Working and idling motion on the movement graphs have three main characteristic sections: the beginning of work (acceleration), smooth movement and gradual braking. In this case, the places where acceleration begins and where braking ends are very important, since at these stages of the crane’s operation increased dynamic loads appear on the assemblies and components of the metal structures of overhead cranes.
To reduce the negative impact on crane mechanisms, we always advise customers to additionally equip beam and overhead cranes with frequency travel converters. Supporting and crane-suspended beams of large load-bearing capacity of long crane spans are especially sensitive to this. The service life of beam cranes using frequency controllers can be extended several times.
Figure 3.2 Electrical circuit for controlling a beam crane (frequency controller)
Table 3.1 - List of electrical circuit elements
The operating principle of an electric hoist.
The diagram of the power part of the electric hoist is shown in Fig. 1. It consists of power contacts of two reversible magnetic starters KM1 and KM2, an electric motor for the winch cable drum M1 and a travel electric motor M2. To prevent the load from lowering spontaneously, the shaft of the M1 motor is equipped with brake pads, and during operation of this motor, the solenoid with the brake coil YB1 opens the pads. Power supply and protection of the circuit from high currents and short circuits is carried out by the QF1 circuit breaker.
The control circuit diagram is shown in Fig. 2. It includes coils of magnetic starters KM1 and KM2 and a push-button station (highlighted in the figure with a dashed line), consisting of double four buttons SB1-SB4 and key SA1.. The control circuit receives power from single-phase network, fuse F1 protects it from short circuits and high currents.
It is not difficult to understand the operation of an electric hoist. First, we supply power to the power contacts of the magnetic starters and the key contact of the control circuit for turning on the QF1 machine. Then we insert the key into the socket of the push-button station, closing contact SA1, thereby bringing the “phase” to the buttons. Next, we will consider the action of the circuit when buttons are pressed.
Let's say that to raise the load up, we press the SB1 button. The current will flow to the KM1v coil through the normally closed contacts of the SB2 button and the KM1n block contacts. the coil will be excited and draw into itself a steel core on which power movable contacts are installed, which close the motor circuit; the brake coil YB1 will turn on and release the winch rotor, the engine will start and the load will go up. This will happen until we release the button. Then the KM1v coil will be de-energized, its contacts will return to their original position; As a result, the M1 engine will stop, and the brake coil will turn off and its pads will press the engine rotor again. To prevent accidental pressing of two buttons SB1 and SB2, SB3 and SB4 at the same time, the circuit provides double blocking. When we press, for example, the SB1 button, the second contact of this button opens the circuit of the second coil of the magnetic starter KM1n; also, when the first KM1v coil is turned on, its block contacts of the same name break the circuit of the second coil, thereby preventing the activation of two “up” and “down” buttons at the same time.
The process of working with the remaining buttons is similar to the first one. To prevent the hook from being raised higher than it should be and creating emergency situations, a limit switch SQ1 is provided, connected to the break of the KM1v coil.
In order to prevent accidents as a result of sticking contacts of starters or other incidents, the QF1 circuit breaker is installed as close as possible to the operator.
Figures 3 and 4 show options for turning on an electric hoist using an additional magnetic starter KM1 and a step-down transformer installed inside the electrical panel of the hoist. The starter is designed to switch the voltage of an electric hoist. Now, in order to remove power from the hoist control starters, it is enough to pull out the key located on the push-button station. Thanks to the transformer, the buttons receive a reduced voltage that is galvanically isolated from the network, which makes the operation of the hoist safer.
Electric hoists are a fairly common load-lifting equipment that has found wide application in various fields. At the same time, for effective and safe work For such a device, it is very important to install it correctly. Not the least role here is played by the process of connecting the mechanism to electrical network. About standard hoist connection diagrams we'll talk about it in this article.
Why is it so important to connect the hoist correctly?
Hoists are universal devices designed to move heavy objects along vertical and horizontal planes. There are quite a large number of different mechanisms of this type. We will not dwell in detail on each of them, since all this is described in the article “”. Let’s just say that models with electric drives have earned their popularity due to their ability to work in high-intensity mode, so they are advantageous to use in construction, as well as in various industries where it is necessary to constantly move heavy objects.
But in order to work quickly and efficiently, it is very important to connect it correctly to the power source.
It is worth noting: Failure to follow certain rules when connecting an electric hoist to the network can lead to complete breakdown of this mechanism, damage to the cargo, as well as harm to the life and health of people. As a result, only specially trained employees who have the necessary experience and skills are allowed to perform this task.
Device connection features
If you are interested 220 volt hoist connection diagram, or a model operating from an industrial electrical network (380 V), then, first of all, you need to read the operating instructions for such a device. It should contain all the necessary information on how to connect the hoist to power, as well as Remote Control by this mechanism.
Before starting work, it is necessary to de-energize the equipment. Only after this can you begin installation. It is very important that the network and control cables are connected in accordance with the device connection diagram.
No matter what you want to connect single-phase hoist without contactor, or any other model, the diagram is located on the side cover of the electrical panel. A copy of the diagram is also indicated in the lifting equipment passport. A typical circuit is shown in the figure below. It contains all the necessary information on how to connect the device and control panel to the electrical power source.
It is worth noting: Even for fairly similar devices, the circuits can differ significantly. Thus, it is necessary to follow the instructions for each specific mechanism. You should not purchase hoists that do not have a connection diagram. It is better to cooperate with trusted suppliers who can provide all the necessary documentation for their models.
How does installation work?
To connect the mechanism, a circuit breaker and fuses are used. Using the first device, you can interrupt the unloaded electrical circuit during work related to electrical wiring. Fuses prevent premature failure of the device in the event of power surges. It is best to place the fuse box in a hard-to-reach place so that others cannot use it. At the same time, working with the block should be simple and convenient.
Power is supplied to the electric hoist using four-core cables. It is important that one of the cores is grounded. In the case of trolley power, it is necessary that a fourth ground wire be present.
As a rule, a flexible cable in rubber insulation is used for the current conductor. If its length is no more than 25-30 meters, then the cable is suspended using rings on a string. This design is distinguished by its simplicity and ease of use. Its diagram is shown in the following figure.
For the string, brass or iron wire with a diameter of 5 millimeters is used. The diameter of the rings (indicated by numbers 3 and 4 in the figure) is 4 cm. It is important that the clamps (5) do not have sharp edges that could rub the cable. Additionally, the clamps are equipped with a tightening bolt (indicated by number 6). As a rule, a rubber pad (7) is used. The optimal distance between pendants is 140-180 centimeters. To prevent cable breakage, a soft metal cable with a diameter of about 2.5 millimeters is fixed at the clamping points. This way the tension will go through it, and not through the cable itself.
If the hoist moves at a distance of 30-50 m, then the cable should be suspended on a roller suspension. In the case when the electric hoist moves within a distance of more than 50 meters, it is necessary to install special high-quality conductive cables.
When using trolley power, it is worth using closed busbars or trolley routes.
It is worth noting: It is best to use cables with increased wear resistance, so they will last you much longer.
After connection, you should check the mains voltage (whether the data obtained corresponds to the parameters specified in the standard table). You can use the mechanisms only if all indicators are within normal limits.
When the device itself has been connected, it is necessary to check the functionality of the button station or remote control with capacitor, with the help of which, as a rule, the hoist is controlled . To do this, press the lift button, and then observe the operation of the mechanism.
Important: if not correct connection it is possible that the load will begin to move downwards. There is nothing wrong with this, you just need to change the location of the connection points.
When all installation work is completed, you should check the integrity of the cables, as well as the possibility of de-energizing the hoist using the power switch. If mechanical or other damage is detected, operation of the equipment is strictly prohibited until all defects are eliminated.
Once again I would like to emphasize the importance of correctly connecting the hoist and the control panel to it. In the absence of special knowledge and skills, it is worth contacting a professional electrician for installation services, who can guarantee high-quality and uninterrupted operation of the hoist in the future.
An electric hoist is a small-sized winch, all the elements of which (electric motor, gearbox, brake, rope drum with threads for laying the rope, a cabinet with starting equipment and other necessary devices) are mounted in one housing or attached to this housing. The electric hoist also includes a chassis for moving along a monorail track and a hook suspension. As a rule, hoists are equipped with a pendant control panel for control from the floor.
Excluding manual hoists and car jacks, electric hoists are the most common lifting machines in the world.
Electric hoists are designed for lifting and horizontal movement of cargo along a monorail track indoors and under a canopy at ambient temperatures from -20 (-40) to +40°C.
Hoists are used as part of suspended and supporting single-beam, cantilever, gantry and other cranes, as well as monorails and independently.
Until the early 90s, the Soviet Union produced a large amount of material handling equipment, but the demand for this equipment always exceeded production. Electric hoists were distributed in 160-180 thousand units. per year (including approximately half of Bulgaria's production), and consumers asked for twice as much. The bulk of electric hoists are used to equip single-girder and jib cranes.
Electrical equipment of electric hoists
Electrical circuit diagrams hoists with different designs have much in common and noticeable differences. They show the principle of design and operation of electrical equipment of hoists.
The hoists are powered from a three-phase alternating current network with a voltage of 380V and a frequency of 50Hz.
On electric hoists they are used without thermal protection with electrical interlocking.
Electric hoists are controlled manually from the floor through a suspension. The design of the push-button station is such that turning on the hoist mechanisms is possible only by continuously pressing the button.
The circuit for switching on the contacts of the control station buttons provides for an electrical interlock, which eliminates the possibility of simultaneous operation of the starters when buttons intended to turn on opposite movements of the same mechanism are simultaneously pressed. This does not exclude the possibility of simultaneous activation of different mechanisms (combining movement with lifting or lowering a load). The presented circuit diagrams retain the designations of the elements used in the operating manuals.
E electric hoist
Electrical circuit diagrams of hoists
Schematic electrical diagram of a hoist with a load capacity of 5.0 tons of the Slutsk PTO plant (developed in 1999).
The electric hoist is equipped with a disc brake, switches for the upper and lower positions of the hook suspension, and an emergency switch for the upper position of the suspension. 42V control circuit.
Schematic electrical diagram of a hoist with a load capacity of 5.0 tons of the Slutsk PTO plant
The power supply to the hoist must be carried out by a four-core cable, one of which is the grounding wire. When trolley feeding the hoist, it is necessary to have a fourth one.
The hoist control circuit operates at a low safe voltage of 42V. which is obtained using a transformer (T) with separate windings connected to phases A and C. Secondary winding transformer (T) must be grounded.
Fuses (F1, F2, F3) protect the transformer windings. The key mark (S) of the PKT-40 control station ensures that the hoist control system is turned on and voltage is supplied to the hoist.
The hoist control buttons (at the station) (S1, S2, S3, S4) provide current supply to the coils (K1, K2, KZ, K4) of the corresponding magnetic starter. Each push-button element, due to its design, provides the first stage of electrical blocking from the simultaneous activation of reversing starters of one motor. The second stage of electrical blocking with the same function is provided by normally closed contacts of the starters (K1, K2, K3, K4). The limit switches (S7, S8) break the electrical circuit of the coils (K2-K1, K4-KZ).
The switches (S7, S8) are acted upon by a rope handler via a mechanical kinematic chain. The switch (S9) duplicates the action of the switch (S7). The brake coil is included in the section of phase B, has two sections, which are wound with two parallel wires, and connected so that the beginning of one (H2) is connected to the end of the other (F1), forming one common terminal, and the other ends of the sections (F1 and F2) connected to diodes (D1 and D2). The power part of the circuit provides power to the motors. This happens using the contact part of the reversing starters K1-K2 and KZ-K4.
Schematic electrical diagram of hoists with a load capacity of 0.25 tons from the Poltava plant (developed in the early 70s)
Electric hoists are equipped with a disc brake, switches for the upper and lower positions of the hook suspension, and an emergency switch for the upper position of the suspension. 42V control circuit
Schematic electrical diagram of hoists with a lifting capacity of 3.2 tons of the Barnaul Machine Tool Plant
The driver of the hoist lifting mechanism is pressed into the drum. The hoists are equipped with a column brake, a switch for the upper position of the suspension (can be equipped with switches for the upper and lower positions of the hook suspension, activated by the rope handler). There is no provision for reducing the control circuit voltage. Basic version with one lifting speed.
Electrical circuit diagram of a 3.2 t hoist with a microdrive
Schematic electrical diagram of hoists with a lifting capacity of 5.0 tons of the Kharkov PTO terminal
The hoists are equipped with a limit switch for the upper position of the hook suspension. Hoists designed for installation on single girder cranes are supplied with a six-button control panel.
Current supply to electric hoists
The current supply to the hoists is carried out in most cases by a flexible cable (Figure 4.8). Trolley feeding is also possible.
A flexible cable (1), used to power the hoist (a four-core flexible copper cable in rubber insulation), perhaps with a current supply length of up to 25-30 m, is suspended using rings on a string (2). This design is shown in the figure.
Current supply to hoists using a flexible cable
The string used is 5 mm steel or brass wire or steel rope. Rings (3 and 4) - 40 ... 50 mm. The clamps (5) must not have sharp edges and are equipped with a coupling bolt (6). The lining (7) can be made of a rubber tube.
The distance between the hangers with a tensioned cable should be in the range of 1400 - 1800 mm. To prevent cable breakage, a soft steel cable with a diameter of about 2.5 mm, the length of which is slightly less than the length of the cable itself, is fixed together with it in the clamps, so that the tension is transmitted through the cable and not through the cable.
Zertsalov A. I.
